Isabel I of Castile, also known as Isabel the Catholic, was born in 1451 and became Queen of Castile in 1474. She is best known for her marriage to Ferdinand II of Aragon, which united two of the largest kingdoms in Spain. Together, they completed the Reconquista by capturing Granada in 1492, marking the end of Muslim rule in the Iberian Peninsula. Isabel's reign was significant for promoting exploration, leading to the sponsorship of Christopher Columbus's voyage that discovered the Americas. She also implemented reforms in her kingdom, strengthening the monarchy and establishing a more centralized government. Isabel died in 1504, leaving a lasting legacy in Spanish history.